Chisels and procedure for insertion of spinal implant in a spinal disc space

ABSTRACT

A chisel with U.V-shaped, saw tooth or other shaped opposing blades is used to form channels in adjacent vertebrae. The chisel has a projection extending from at least one of the top and bottom surfaces to limit depth of penetration into the vertebrae. A guide member may be attached to the forward tip of the chisel to guide the chisel into the disc space to uniformly chisel both adjacent vertebrae simultaneously to form a channel in the vertebrae. The so formed channels serve as sa guide for a second chisel having no guide member. The second chisel, which may be a box chisel, is used to complete the channels to the desired depth to receive an associated implant, typically of cortical bone. Other embodiments are disclosed in which a two step box chisel has a retractable guide member for initially guiding the chisel as it forms partial channels in the vertebrae disc space. The guide member is then retracted and the channels formed to the desired depth. The chisels include guide member pins which serve to both limit the extension and retraction of the guide member and also to serve to limit the depth of penetration of the chisel, physically and visually. The guide member may be retracted with a rotatable knob and a threaded engaged rod or with an axially displaceable pin and rod assembly attached to the guide member. A procedure for using the chisels is also disclosed.

This application claims the benefit of, is a continuation in part of andincorporates by reference in its entirety provisional application Ser.No. 60/397,232 filed Jul. 19, 2002.

This invention relates to spinal implant chisel tools and method ofpreparing the spinal disc space employing such chisels for insertion ofimplants into the intervertebral disc space.

Of interest is commonly owned U.S. Pat. No. 6,277,149 entitledRamp-Shaped Intervertebral implant incorporated by reference herein.

Spinal implants, sometime referred to as grafts, are in wide use andtypically comprise non-bone physiologically compatible metal or othernon-bone materials or bone. Reference is made to the aforementionedpatent for description of a bone implant. The method of preparing thesite of the spine for spinal implant insertion involves a variety oftools and individual processes. The prior art is replete with differentimplants, implant insertion tools and procedures for insertion of spinalimplants with such tools.

For example, U.S. Pat. No. 6,096,038 to Michelson discloses distractiontools for distraction of adjacent vertebrae, implants for insertion intothe spine, drills for drilling the intervertebral site to prepare thesite for implant insertion, other tools used for preparing the discspace by cutting bone, a driver extraction instrument for extracting animplant driver tool from the spinal disc space and generally disclosessurgery for providing an integrated discectomy, fusion and interbodyinternal spinal fixation.

U.S. Pat. No. 6,174,311 to Branch discloses implants formed from donorbone for use in lumbar interbody fusion procedures and instruments forperforming such procedures. Specific implants and instruments aredisclosed for inserting the implants and for preparing theintervertebral space to receive the implants. Disclosed is a box chiselthat has a hollow core that is somewhat rectangular.

Also disclosed is a plane scraper and a rotatable cutter. This lattercutter has multiple cutting arms defining a cavity therebetween forreceiving cutting debris. Each arm has at least two cutting blades. Theblades extend axially between the handle and the cutting end. The boxchisel cutting edges are normal to the axial direction of the tool in adirection from the handle to the box cutter, whereas the rotating cuttercutting edges are parallel to the axial direction. In use, this rotatingcutter tool cuts bone by rotation of the tool about its longitudinalaxis.

In another embodiment, a box chisel is disclosed that has a depth stopto prevent the chisel from cutting deeper into the disc space than apredetermined depth and includes depth indicator marks to indicate thedepth of penetration of the chisel. Implants and implant holders arealso disclosed. This patent is incorporated by reference in itsentirety.

U.S. Pat. No. 4,697,586 to Ganzale discloses a combined chisel-guidesurgical instrument. The instrument is for performing osteotomy andother procedures on the human vertebra and comprises at least onelongitudinally directed and movable chisel each including at least onefront cutting edge for penetrating into the vertebra, a longitudinallydirected guide including a front guide tip being locatable withinintervertebral space for accommodating and directing the motion of thechisel cutting edges into the vertebra, a handle fixedly secured to rearextension of the guide for directing and placing the guide tip into theintervertebral space, a front impact block member connected to the rearextension of the chisel, an intermediate longitudinally directedcylindrical member connected to the rear end of the front impact blockmember, a rear impact cylindrical member fixedly connected to the rearend of the intermediate cylindrical member, and a longitudinally movableimpact hammer accommodated by the intermediate cylindrical member.

The impact hammer causes forward penetration of the chisel front cuttingedge to the desired penetration depth and the impact hammer impacts thecylindrical member to cause rearward retraction of the chisel and thehandle causes rearward retraction of the guide tip from the disc space.The guide tip serves as a depth gauge. Surface extensions at the rear ofthe guide tip prevent penetration deeper than the anterior longitudinalligament.

The chisel slides along a track surface on the guide. A two chiselembodiment is disclosed wherein one chisel penetrates one vertebra ortwo chisels are used to penetrate two vertebra. The impact hammer isoperative with the one chisel or two chisels which are arranged inmirror image fashion to each other and are each disclosed as U-shape inone embodiment.

The guide tip is inserted into the disc space first. The chisel is thenslid onto the handle and along a surface of the guide until the cuttingedges rest on the dorsal aspect of the vertebral space. The impacthammer is used to insert the cutting edges into the vertebral plates.The chisel is withdrawn with the hammer leaving the guide tip insertedin the disc space. The tip is then withdrawn. In a two chisel mode, theguide tip is inserted first and then either or both chisels may beoperated at the same time wherein the chisels may be driven one at atime or together. The guide tip is removed after the chisels areremoved. The cutting edges are normal to the insertion direction andlongitudinal axis of the instrument similar to a box chisel.

U.S. Pat. No. 4,736,738 to Lipovsek et al. discloses an instrument kitand method for performing posterior lumbar interbody fusion. The kitincludes first and second chisels and first and second shafts, aretaining ring with a set screw, an extraction hammer, a tamper and ahook. The first and second chisels each have a U-shaped blade and ashoulder between the blade and shaft. The second chisel is larger thanthe first chisel to enlarge the groove made by the first chisel. A stopprevents the shaft from slipping through the intervertebral space. Theshoulders limit the depth of penetration of the chisels. The firstchisel is used first and then withdrawn from the disc space. Then thesecond chisel is inserted to enlarge the channel formed by the firstchisel. The chisel edges are coplanar and at right angles to thelongitudinal axis of the instrument shaft.

U.S. Pat. No. 695,783 discloses a coping tool or chisel having a contourof molding to be cut and comprises a double chisel. A guide piece slidesin a vertical recess in a frame of a mortising machine. A guide pieceand gauge piece supported by the guide piece are fixed to the chisel.When a comer of the mold engages the guide piece the required depth iscut.

U.S. Pat. No. 740,937 discloses a chisel with a forward end withprojecting spurs having rounded cutting edges. A forward end portion hasa cutting edge.

U.S. Pat. No. 3,848,601 to Ma et al. discloses an interbody fusionapparatus including an intervertebral mortising chisel with an innerdrill bit. The sides of the chisel have stops. The cutting edges arecoplanar and lie in a plane normal to the longitudinal axis of the shaftforming what Is generally referred to as a box chisel in that the edgesof the chisel resemble a box shape.

U.S. Pat., No. 5,1722,977 to Wilhelmy discloses a quadrilateralosteotome for use with a guide spacer. The guide spacer is inserted intothe disc intervertebral space and while inserted, the chisel is theninserted to perform the bone cutting process guiding the chisel at thistime. The guide spacer is received within the chisel hollow core andguides the chisel during its use. The chisel is shown as a box chisel.

U.S. Pat. No. 6,224,607 to Michelson discloses an instrument set thatincludes an extended guard for providing protected access to the discspace, and the adjacent surfaces of the adjacent vertebral bodies, aguide insertable into the guard, and a bone removal device such as adrill insertable into the guide.

The present inventors recognize a need for an improved chisel andprocedure for preparing a spinal disc space for receiving a spinalfusion implant.

A chisel for preparing adjacent vertebrae for insertion of a spinalimplant into the disc space defined by the vertebrae according to anaspect of the present invention comprises a handle and a shank having alongitudinal axis and distal and proximal ends, the handle being securedto the distal end. A bone cutting blade is attached to the shankproximal end and having a cutting edge lying in a plane for forming achannel in one of the vertebrae, the blade extending transverse to thelongitudinal axis and having a bone cutting edge facing in a proximaldirection, the blade edge being non-linear in shape and having an apexin top plan view, the cutting edge having first and second cuttingcoplanar portions that each taper in the proximal direction.

In one aspect, the first and second cutting edge portions taper towardeach other terminating at the apex.

In one aspect, the first and second portions of the blade aresymmetrical relative to the axis and the apex lies on the axis.

In a further aspect, the shank at the proximal end is solid with arectangular cross section, the shank having peripheral top and bottomsurfaces and peripheral first and second side surfaces, furtherincluding a solid rectangular chisel guide member one piece with andfixedly secured to the shank and extending from the shank proximal endcoextensive with the outer side surfaces juxtaposed with and beyond theblade apex.

In a still further aspect, the blade has a top surface that iscoextensive and coplanar with the shank top surface and a cutting edgethat tapers distally toward the shank and toward the guide member.

In a further aspect, the shank has peripheral top and bottom surfaces,further including a projection extending from at least one of the topand bottom surfaces and spaced distally from the blade edge for abuttingadjacent vertebrae during use of the chisel to limit the depth ofpenetration of the chisel into the vertebrae disc space.

In a further aspect, the projections each comprise a portion of a pinInserted in a through bore in the shank.

In a further aspect, the shank has a groove and a shoulder adjacent tothe distal end thereof, the handle including a quick release sleevearranged to be releasable secured to the groove and shoulder.

In a further aspect, the sleeve includes a pin for mating with theshoulder to preclude relative rotation of the sleeve and handle to theshank.

In a further aspect, the handle includes a shaft portion with aplurality of balls arranged in annular array about the shaft portion forradially displacement in corresponding bores, the sleeve having astepped bore having first and second segments for receiving the shaftportion along the axis, the first segment for allowing the balls alignedtherewith to be radially aligned with and external said groove in afirst axial position of the sleeve to permit the shank to be disengagedfrom the shaft portion and the second segment for urging the balls intothe groove in a second axial position to releasably lock the shaftportion to the shank.

In a further aspect, including resilient means for resiliently urgingthe sleeve to a quiescent second position to normally lock the handle tothe shank in the quiescent second position.

In a further aspect, the shaft portion and the sleeve have juxtaposedspaced shoulders, the resilient means comprising a spring between andabutting the shoulders.

In a further aspect, the shank has a hollow core at the proximal endfacing in the proximal direction, further including a chisel guidemember movably attached to the shank for selectively extending from thecore in a direction toward the proximal end and retracting into the corein a direction toward the distal end.

In a further aspect, the guide member has a through slot, the shankincluding a pin fixed to the shank and movably attached to the guidemember in the slot so that the guide member can axially displace in thecore in opposite directions along the longitudinal axis toward and awayfrom the proximal end.

In a further aspect, the pin protrudes from the shank to provide avisual indication of the depth of penetration of the chisel into thevertebral disc space and provides depth limit means for abutting atleast one of the vertebrae forming a stop for the chisel.

In a further aspect, guide member displacement means are included forselectively manually respectively extending and retracting the guidemember from and into the core.

Preferably the displacement means comprises a first rod attached to theguide member and having a rod portion extending into the handle, and arod displacement arrangement coupled to the rod portion for axiallydisplacing the first rod toward and away from the proximal end.

In a further aspect, the rod is releasably attached to the guide member.

In a further aspect, threads rotationally couple the rod to the guidemember, and a knob is connected to the rod for rotating the rod relativeto the guide member, the knob having a fixed axial position on thehandle such that rotation of the knob displaces the guide member via thethreaded engagement of the rod to the guide member.

In a further aspect, the knob is keyed to the rod to rotate the rod withrotation of the knob.

In a further aspect, the handle has a slot receiving the knob, thereceived knob for manual engagement by a thumb.

In a further aspect, the shank at the proximal ends has at least onethrough slot for receiving bone chips during use of the chisel.

In a further aspect, the rod displacement means includes a transverselyextending second rod attached to the first rod at the first rod enddistal the guide member and detent means attached to the handle forreceiving the second rod for selectively releasably securing the secondrod in guide member retracted and extended positions.

In a further aspect, the detent means comprises a slot in the handle forreceiving the second rod, the slot having first and second axiallyspaced channels each for selectively receiving the second rod.

In a further aspect, a sleeve is included over the handle at the slotincluding a further slot juxtaposed with the handle slot

In a method for preparation of a disc space for insertion of a spinalimplant into the disc space between adjacent vertebrae, the stepsaccording to a further aspect of the present invention comprisesinitially removing a first portion of at least one of two adjacentvertebrae of the disc space with a first chisel with an extended guidemember to form at least one partial channel in the at least onevertebra, the guide member for bearing against the adjacent vertebraeand guiding the chisel during the removing; and then removing a furtherdeeper second portion of the at least one adjacent vertebrae with asecond chisel guided by first channel portion, the second chisel havingno guide member, to form the at least one partial channel into at leastone complete channel for receiving a spinal implant inserted into thedisc space, the further portion being aligned with and extending the atleast one channel to a depth into the disc space an amount sufficient toform the complete channel.

In a further aspect, the method includes forming the at least onepartial channel and the at least one complete channel in each of theadjacent vertebrae with the same chisel.

In a further aspect, the removing a further portion of the at least oneadjacent vertebrae with a second chisel includes retracting the guidemember of the first chisel into the first chisel to form the firstchisel into the second chisel.

In a further aspect, the method includes the removing a further portionof the at least one adjacent vertebrae with a second chisel includesremoving the first chisel from the formed at least one partial channelin the at least one vertebra and then inserting the second chisel intothe formed at least one partial channel wherein the at least one partialchannel guides the second chisel during the insertion.

IN THE DRAWING

FIG. 1 is an isometric view of a portion of the lumbar spine with a pairof implants inserted posteriorly into the disc space according to aprocess of the present invention;

FIG. 2 is a side elevation view of the spine of FIG. 1;

FIG. 3 is a side sectional elevation view of a representative spinalimplant that may be inserted into the disc space prepared by theprocedure of the present invention;

FIG. 4 is a plan view of the implant of FIG. 3;

FIG. 5 is an isometric view of a rotating scraper which may be used inthe process of the present invention;

FIG. 6 is a sectional end elevation view of the scraper of FIG. 5showing the blade portion of the scraper;

FIGS. 7 and 8 are side and plan elevation views of a paddle typedistractor that may be used in the process of the present invention;

FIGS. 9 and 10 are respective side elevation views of a trial useful inthe procedure of the present invention wherein FIG. 10 is a moredetailed view of the measuring end of the trial of FIG. 9;

FIG. 11 is a top plan view of a chisel according to an embodiment of thepresent invention with a fixed guide member;

FIGS. 12 and 13 are respective side elevation and isometric views of thechisel of FIG. 11;

FIG. 14 is a side elevation sectional fragmented view of the chisel ofFIG. 11 taken along lines 14-14;

FIG. 15 is an isometric view of a quick release handle for use with thechisels of FIGS. 11-13 and FIGS. 16-17;

FIG. 16 is an exploded side elevation view of a chisel according to afurther embodiment of the present invention;

FIG. 17 is a side elevation view of the assembled chisel of FIG. 16;

FIGS. 18 and 19 are isometric views of a chisel and chisel tip endshowing two blade cutting edges of a chisel for use with a processaccording to a further embodiment of the present invention

FIGS. 20 and 21 are respective side sectional fragmented elevation viewsof the assembled handle and chisel of FIG. 17 in respective handlelocked and unlocked states;

FIGS. 22 and 23 are respective sectional views of the embodiments ofFIGS. 20 and 21 taken at respective lines 22-22 and 23-23;

FIGS. 24-25 are respective isometric AND side elevation and views of achisel with a fixed guide member according to a further embodiment ofthe present invention;

FIG. 26 is an isometric exploded view of a chisel with a retractableguide according to a further embodiment;

FIG. 27 is a fragmented side elevation partially in section of a chiseltip portion of the chisel of FIG. 26;

FIG. 28 Is a sectional end elevation view of the portion of FIG. 27taken at lines 28-28;

FIG. 29 is a fragmented side elevation view of the handle, shaft andchisel portions of the chisel of FIG. 26;

FIG. 30 is a more detailed side elevation view of the chisel cutting endof the chisel of FIG. 29;

FIG. 31 is is a side elevation view of the chisel guide member of thechisel of FIG. 26;

FIG. 32 is a sectional elevation view of the member of FIG. 31 taken atlines 32-32;

FIG. 33 is an end elevation sectional view of the member of FIG. 31taken at lines 33-33;

FIG. 34 is a fragmented side elevation view of a threaded rod for usewith the chisel of FIG. 26;

FIG. 35 is a sectional view of the rod of FIG. 34 taken at lines 35-35;

FIG. 36 is an end elevation view of the knob used with the chisel ofFIG. 26;

FIG. 37 is a sectional view of the knob of FIG. 36 taken at lines 37-37;

FIG. 38 is an isometric view of a chisel according to a furtherembodiment of the present invention;

FIG. 39 is a sectional elevation view of the chisel portion of FIG. 46taken along lines 39-39;

FIG. 40 is a fragmented side elevation view of a portio of the handle ofthe chisel of FIG. 38;

FIG. 41 is an exploded isometric view of the chisel of FIG. 38;

FIG. 42 is a fragmented top plan view of the chisel shaft of FIG. 38;

FIG. 43 is a more detailed side elevation view of the handle portion ofthe chisel of FIG. 41;

FIG. 44 is a sectional elevation of the embodiment of FIG. 40 takenalong lines 44-44;

FIG. 45 is an isometric view of the shaft of the chisel of FIG. 42;

FIG. 45 a is an isometric view of shaft of a chisel similar to the shaftof the chisel of FIG. 45 except the shaft of FIG. 45 a has V-shapedcutting edges the same as the cutting edges of the chisel of FIGS. 11-13and is arranged to receive a retractable guide as shown for example forthe chisel of FIG. 38 rather than a fixed guide as shown in theembodiment of FIGS. 11-13;

FIG. 45 b is an isometric view of shaft of a chisel similar to the shaftof the chisel of FIG. 45 except the shaft of FIG. 45 a has cutting edgesthat are inclined relative to the longitudinal axis of the shaft and isarranged to receive a retractable guide as shown for example for thechisel of FIG. 38;

FIG. 45 c is a top plan view of the blades of the chisel of FIG. 45 b;

FIG. 46 is a fragmented sectional side elevation view of the chisel endof the chisel of FIG. 45;

FIGS. 47 and 48 are respective side elevation view of the chisel of FIG.38 showing the chisel with its guide member retracted and extended;

FIGS. 49 is a side elevation view of the sleeve portion of the chisel ofFIG. 41;

FIG. 50 is a sectional elevation view of the sleeve of FIG. 49 takenalong lines 50-50;

FIG. 51 is an isometric view of a portion of the human spine during thespinal preparation process for receiving the spinal implants of FIGS. 1and 2;

FIG. 52 is a side elevation view of the human spine showing a trial toolused to determine the size of the disc space after preparation of thedisc space prior to insertion of the implant;

FIG. 53 is an isometric view of the human spine showing a laterchiseling step using the chisel of FIG. 11 in the process of FIG. 51;and

FIG. 54 is a side elevation view of a chiseling step in the spinal discpreparation process using the chisel of FIGS. 18 and 19 in a stepsubsequent to the step of FIG. 53.

In FIGS. 1 and 2, two spinal implants 2 and 4 of the configuration ofthe implant of FIGS. 3 and 4, are shown implanted into the disc space 6between adjacent vertebrae V1 and V2. The implants 2 and 4 are mirrorimages of each other and a description of one is representative. Thedisc space 6 has been prepared for receipt of the implants according tothe procedure described later herein. The implants 2 and 4 are eachlocated in corresponding channels 8 and 10, and 8′ and 10′,respectively, prepared according the procedure to be described. Theimplants 2 and 4 have been inserted from the posterior approach. In thealternative, these implants.may be inserted from the anterior, theantereo-lateral or any other approach relative to the spine as desired.

A further tool utilized in inserting the implants 2 and 4, are trialswhich determine the size of the disc space between the channels 8 and 10or 8′ and 10′, FIGS. 1 and 2.

In FIGS. 3 and 4, representative implant 2 is formed of cortical bone ina known manner, for example, as disclosed in the aforementioned commonlyowned and Branch patents. The outer surfaces are machined to the shapeas shown. The implant has a longitudinal axis 14 and terminates atopposite ends in planar respective posterior and anterior end surfaces16 and 18. The implant has serrated opposing surfaces 20 and 22 forengaging the associated adjacent vertebra.

The serrations on surfaces 20 and 22 are formed by parallel groovesforming respective saw teeth 24 and 26. The side wall surface 28opposite the cavity 12 is convex arcuate. The implant may have taperedsurfaces 20 and 22 at the anterior end at surface 18 as shown by dashedlines 32. A bore 30 may be formed in surface 16. Bore 30 receives aninsertion tool to assist in insertion of the implant. The bore 30 may besmooth walled or threaded to receive an insertion tool rod (not shown).The opposing surfaces 20 and 22 are wedge shaped to conform to thelordotic shape of the intervertebral space tapering to the widest regionat the anterior end of the implant. Side surfaces 34 and 36 are flat andcoplanar.

In FIGS. 7 and 8, a paddle distractor 35 of known configurationcomprises a shank 37 and the distractor working end 38. End 38 has arelatively wide flat surface 39 and a relatively narrow side wallsurface 41. The tip 43 may taper somewhat. A similar distractor isdisclosed in U.S. Pat. No. 5,957,836 to Johnson and in an articleentitled Posterior Lumbar Interbody Fusion Technique using the VariableScrew Placement Spinal Fixation System by John W. Brantigan et al.Spine: State of the Art Reviews, Vol. 6, No. 1, pages 177-198 and inparticular at page 181, January 1992, Hanley & Belfus, Inc.,Philadelphia, Pa, wherein the tool is referred to as a spreader, bothdocuments being incorporated by reference herein.

A further tool used during the implant insertion process is a trial suchas trial 40, FIG. 9. The trial 40 has a shank 42, a measuring tip 44 anda handle 46. The tip 44, FIG. 10 has a body 46 which is wedge shaped tomatch the wedge configuration of the implants 2 and 4 and so on. Theanterior measuring end 48 is tapered at insertion chamfers 50 whichfacilitate the insertion of the trial into the disc space in theposterior direction. The tip 44 tapers and converges toward theposterior end 52 and matches the taper of the implants such as implants2 and 4, for example. Holes 54 are utilized to assist the surgeon invisually identifying the depth of insertion of the trial tip 44. The tip44 engages the channels 8, 10, or 8′, 10′ across the prepared disc space6, FIGS. 1 and 2. The implants, distractor and trial are available issets of matching dimensions so that a given distractor and trialdimensions correspond generally to a given implant dimension. The trialis used to determine the size of the disc space between the channels 8,10 and the surgeon then selects the implant of a given dimension thatmatches the fit with the trial. The distractors are made in sets ofdiffering dimensions also to assist in utilizing the selected dimensionsof the associated trial. This will all be explained more fully below inconnection with the procedure for preparing the disc space.

In FIGS. 5 and 6, a further tool utilized in preparing the disc space isa rotatable scraper 56. Scraper 56 has a shank 58 connected at one endto a handle (not shown) and a vertebrae scraping tip 60 at the otherend. In FIG. 6, the tip 60 has two opposing planar surfaces 62 and 64.Surface 62 terminates in bone cutting edges 66 at opposite sides of thetip. Surface 64 terminates in bone cutting edges 68 at opposite sides ofthe tip. A channel 70 is between each of edges 66 and 68 on each side ofthe tip 60. During use, the scraper 56 is rotated about its longitudinalaxis 72, FIG. 5.

In FIGS. 11-17 a chisel 74 according to a first embodiment is shown.Chisel 74 has a shank 76 and a chisel end 78. A quick release handle 80,FIGS. 15-17, is releasably attached to the shank 76. In FIGS. chisel 74end 78 is a solid rectangular metal, preferably stainless steel. Theshank 76 is circular cylindrical. The end 78 has opposing parallelplanar top and bottom respective surfaces 82 and 84. A cylindrical bore86 is formed in the surface 82. The bore 86 receives a color coding disc88 which identifies the dimensions of the blades 92 and 94 at the chiseltip 90. A pin 96 passes through a through bore in the chisel end 78extending beyond each of the top and bottom surfaces 82 and 84.

The blades 92 and 94 are identical mirror images of each other and arejuxtaposed with each other. The blades have cutting edges 92′ and 94′coplanar with the top and bottom surfaces 82 and 84, respectively. Inthis embodiment, the edges 92′ and 94′ are each non-linear in that theyare V-shaped in plan view with the center of the Vee lying on a planecontaining the longitudinal axis 98, FIG. 11. Each edge 92′, 94′ has twoportions that are inclined to the plane normal to the drawing sheetcontaining the axis 98 at equal angles at an acute angle. The edges 92′and 94′ terminate at an apex A on the plane containing the longitudinalaxis 98. The sides 100 of the edges of the blades 92 and 94 taper towardthe plane that is normal to the drawing sheet and which plane containsthe longitudinal axis 98, FIG. 12. The sides 100 are preferablysymmetric with that plane. In the alternative, the angles formed by theedges 92′ and 94′ with the axis 98 need not be equal. In a furtheralternative, the apex of the V may be inversely located to that shown sothat it forms a V-shaped channel with the edge portions and the twosides of the V taper toward the distal end and toward the apex. In thisembodiment, the two edge portions taper from the apex toward the chiselside walls and toward the proximal end.

In the alternative, the edge of each blade may be U-shaped in plan viewsimilar to the view of FIG. 11. The U-shape is thus curved and may jointhe sides 104 in a gradual taper. In this case, the U-shaped edges havean apex that is curved rather than pointed in plan view. Thus a tangentto opposite sides of the U intersect the corresponding side walls suchas walls 104, FIG. 11, of the chisel at an acute angle. The U shape edgemay be symmetrical or asymmetrical about axis 98, FIG. 11. Also thesides of the U terminate centrally at the apex of the U. As used hereinand in the claims the term “blade” is intended to include at least thecutting edge(s) of the chisel.

In a further alternative, the cutting edge may comprise a series of V orU-shaped cutting edges to form a generally saw tooth pattern in the planview. These various shaped cutting edges generally may be non-linear,i.e., curved as in U-shaped, V-shaped or other non-linear shape in topplan view as seen in FIG. 11, for example. Thus the term non-linear edgemeans that the cutting edge from end to end, i.e., from side wall 104 toopposite side wall 104, has at least a non-linear portion (a change indirection) in the plan view of the edge as edge 92′, FIG. 11. Thatnon-linear portion may include linear sub-portions such as formed byedge portions on opposite sides of the apex of a V-shaped edge, FIG. 11.

Where the term calling for the edge to intersect the longitudinal axisis used, the term edge refers to the plane containing the edge, such asthe plane of the drawing sheet, FIG. 11. Thus the edge 92′, FIG. 11,lying in the plane of the drawing sheet of FIG. 11, intersects the planecontaining the longitudinal axis 98, the latter plane being normal tothe drawing sheet. The edges (or the linear portions of the edges as inV-shaped edges) of all of the chisels disclosed herein lie in and definea plane such as the edges 92′, 94′, FIGS. 11 and 12. That plane isnormal to the plane of the drawing sheet in FIG. 12 and parallel to thedrawing sheet in FIG. 11. The non-linear edges may also be undulating orother shapes. A U-shaped edge (not shown) thus has a tangent theretothat intersects the sides of the chisel such as sides 106, FIG. 11. Theterm “tapering edges” refers to both linear and curve edges.

A guide member 102 extends from the end 78 beyond the edges of theblades 92 and 94 and is one piece integral with the end 78. The guidemember 102 has opposite sides 104 that are coextensive and coplanar withthe sides 106 of the end 78. The guide member 102 has parallel top andbottom surfaces 108 and 110, respectively, FIG. 14. The member 102 haschamfers at the top and bottom surfaces thereof at the leading edge 112to facilitate insertion into the disc space between adjacent vertebrae.

The shank 76, FIGS. 11 and 12, has an annular groove 114 at the distalend 116 and a flat radially inwardly extending step 118 in the regionbetween the groove 114 and the end 116. The step 118 has a shoulder 119.The shank 76 at the groove 114 and step 118 receives quick releasehandle 80, FIGS. 15-17 and 20-23.

The quick release handle 80 includes a handle portion 120 and an axiallymovable sleeve 122. In FIGS. 20 and 21, the handle portion 120 has acircumferential radial inward step 124 forming an axially facingshoulder 126. The step 124 terminates in a further radial inward planarstep 128 having an axially facing shoulder 130. A pin 132 is attached bypress fit to the sleeve 122 and is captured to the handle portion inchannel 128 by shoulders 130 and 131.

The sleeve 122 has radially outwardly formed steps 134 and 142 formingan intermediate region 144 of smaller diameter than that of steps 134and 142. Step 134 has a shoulder 136. A coil compression spring 138 issecured between the step 124 of the handle portion 120 and step 134 ofthe sleeve 122 and is captured between shoulders 126 of the handleportion 120 and 136 of the sleeve 122. The sleeve 122 has a collar 140.

With the sleeve 122 engaged with the shank 76 as shown in FIGS. 20 and21, the pin 132 is adjacent to the step 118 on the shank 76 and islocated in the channel 128 of the handle portion 120.

The pin 132 abuts the flat surface of the step 118 of the shank 76 andthe base surface of the channel 128 of the handle portion. The pin 132prevents relative rotation of the shank 76 to the handle portion 80.

The handle portion 80 has a bore 146 that axially receives the shank 76.A set of three radial through holes and counter bores 148 are in thehandle portion 80 in communication with the bore 146. Three stainlesssteel balls 150 are each free floating in a corresponding counter bore148, but captured to the handle portion 80 by smaller through holes onthe radial inside of the counter bores and by sleeve 122 on the radialoutside of the counter bores. The balls selectively can protruderadially inwardly into the bore 146, FIG. 20, from the counter bores148, or radially outwardly from the counter bores 148, FIG. 21.

The balls 150, in the position of FIG. 21, are flush with the outersurface 152 of the shank 76. In this position the balls 150 protruderadially outwardly from the counter bores 148. The balls, in theposition of FIG. 20, protrude radially inwardly from the counter bores148 engaging the annular groove 114 on shank 76.

In operation of the quick connect handle, the sleeve 122 is in thenormal position, FIG. 16, with the balls protruding radially inwardlyfrom the counter bores 148 into bore 146 by the inner surface of theintermediate region 144. To engage shank 76, the sleeve 122 is pulled byhand toward the handle portion 120 SO that the balls are free toprotrude radially outwardly from the handle portion 80 segment 154surrounding the bore 146 into step 142. The shank 76 is inserted intothe bore 146 as shown in FIG. 21. The shank 76 outer peripheral surfaceforces the balls radially outwardly into the step 142 in this position.When the shank 76 is fully inserted into the bore 146 of the segment154, FIG. 20, the balls are aligned with the groove 114 in the shank.The radially inwardly extending groove 114 permits the balls 150 toprotrude radially inwardly at this location into the groove 114,engaging the handle to the shank. The spring 138 with manual release ofsleeve 122, forces the sleeve 122 to the right in FIG. 20 forcing theballs 150 radially inwardly into the groove 114. In this position of thesleeve, the balls 150 are locked radially inwardly in the groove 114 bythe sleeve 122. The balls can not move radially outwardly at thislocation due to the sleeve intermediate region 144 locking the ballsradially inwardly in engagement with the groove 114. In this position,the sleeve and handle portion 80 are connected to the shank which cannot rotate relative to the sleeve due to the pin 132.

To release the handle portion 80 from the shank, the sleeve is retracteduntil the step 142; is positioned as in FIG. 21. The shank at thisposition of the sleeve, can now be withdrawn to the right by displacingthe balls 150 outwardly into the step 142 and out of the groove 114. Therelease position of the handle portion 80 is shown in FIG. 17 and thelocked position is shown in FIG. 16.

The pin 96 projections from the chisel end 78, FIG. 12, limit the depthof penetration of the chisel into the vertebrae to form a partialchannel in each vertebra.

In FIGS. 18 and 19 a box chisel 156 has a handle 158, a shank 160 and achisel tip 162. In FIG. 19, the chisel tip 162 is rectangular in crosssection and has a body 164 with an axial extending slot 166 forreceiving bone chips during chiseling. The body has apertures 168 for sindicating depth of penetration into the vertebral disc space. The tip162 has two blades 170 and 172 in parallel and lie in a plane that isnormal to the longitudinal axis 174 of the shank 160. The tip 162 hasholes 168 for indicating depth of penetration into the intervertebraldisc space. The blades 170 and 172 have parallel first sides 174 and 176and tapered second sides 178,180, respectively. The core 182 is hollow.A color coding ring 184 is attached to the handle to correspond thechisel to the same set as the other tools which are all color coded withthe same color for a given set of tools for a given implant size. Thetwo blades 170 and 172 engage the adjacent vertebrae previously engagedby the chisel 15 blades of the chisel 74 of FIGS. 11-13. The blades ofthe chisels 74 and 156 are arranged to form channels in the adjacentvertebrae of the same channel spacing across the disc space. The chisel156 is dimensioned the same as the chisel 74 so as to lengthen the depthof channels formed by chisel 74 into the vertebrae.

The guide member 102 of the chisel 74 guides the chisel into the discspace so as to cut equal amounts of bone from the adjacent vertebrae andto center the chisel in the disc space between the adjacent vertebrae.The member guides the chisel 74 to form channels of partial depth intothe vertebrae. This is referred to as a start chisel.

The chisel 156, FIGS. 18-19 is referred to as a finishing chisel as itfinishes the channels in the vertebrae started by chisel 74. Thechannels formed by chisel 74 serve as a guide for the finishing chisel156 so as to align the finishing chisel and form smooth complete fullyformed channels in the adjacent vertebrae. No guide member is used onthe chisel 156 as it is guided by the partially formed channelsinitially produced by the chisel 74. The blade spacing of the twochisels as well as their transverse blade widths are otherwise the same.

In practicing the posterior approach procedure with the aforementionedtools, the surgeon uses the posterior approach to reach the site inquestion and performs a discectomy. Sequentially sized distractors 35,FIG. 51 are then used to increasingly distract the vertebrae to theappropriate height h. The distractors 35 are first inserted with theirflat wide surfaces 39 parallel to the vertebrae in a known manner. Afterinsertion into the disc space the surgeon then rotates the distractor sothat the flat blade end 38 is positioned between the adjacent vertebraeas shown in FIG. 51.

Optionally, the rotating scraper 60, FIGS. 5 and 6, are used to cleanthe disc material from the disc space and to prepare the vertebrae forthe next step of forming the channels. Next, the chisel 74, FIGS. 11-13and 15-17 is used to form a channel in each of the vertebrae. Anappropriate size chisel is selected by the surgeon with a correspondingsize distractor in place, the chisel is tapped into the contralateralside with the guide member 102 first inserted into the disc space D,FIG. 53. The guide member 102 has a height that is slightly smaller thanthe disc space D height h (FIG. 51). The chisels 74 are supplied in setsof differing dimensions to correspond to the other tools being used inthe procedure and implant to be inserted. The implants are also suppliedin sets of differing dimensions to accommodate differently dimensioneddisc spaces D.

The guide member 102 helps ensure even endplate removal from bothvertebrae. The guide pin 96 protruding from the chisel allows insertionof the chisel halfway into the vertebrae while preventing the extendedguide from going too far into the space D. For example, if the vertebraeare distracted using a 7 mm distractor on one side, a 9 mm guided boxchisel is used to create the bleeding bone necessary for fusion. Theguide member has a height of about 7 mm or slightly less.

The guide member keeps the chisel centered in the disc space D withrespect to the top and bottom vertebrae, so that the same amount ofvertebral end plate is chiseled and removed on both the top and bottomsurfaces of the vertebrae. The guided chisel 74 is impacted into oneside of the disc space while the distractor is in place on the otherside.

In a further example, if a 9 mm distractor is used, a 11 mm chisel isused on the contralateral side. The guide member 102 for this chisel hasa height of about 9 mm or slightly less. In the alternative, with a 9 mmdistractor in place on one side, a slightly smaller chisel can be used,for example, a 9 mm chisel with a guide member height of 7 mm. In anycase, the chisel is impacted into the disc space until the pin 96 abutsthe edge of the vertebral bodies. The pin 96 serves as visual andpositive stop for the chisel. The chisel is then removed with a slaphammer as known in this art, which comprises a movable mass attached toa shaft which may be threaded to the handle of the chisel such as chisel74. The handle has mating threads (not shown) for receiving the slaphammer. The channel is about 10 mm long in this example by chiseling upto the pin 96 stop. The pin 96 may be about 20 mm to the tip of theguide member 102.

At this time, the finishing chisel 156, FIGS. 18 and 19, is theninserted into the partially created channel, FIG. 54. This instrument isvirtually identical in exterior dimensions to the box chisel 74 with theguide member 102 except the blades 92 and 94 of the chisel 74 areV-shaped and the blades of the chisel 156 are straight across normal tothe longitudinal axis of the tool. The partial channel created by thechisel 74 serves as a guide for the chisel 156 to keep this chiselapproximately centered within the disc space D relative to the heightdimension h (FIG. 51). Chisel 156 is impacted until the desired depth isobtained. Typically this depth is 3 mm longer than the length of theimplant being inserted.

The chisel 156 is then removed using a slap hammer attached to thechisel (not shown) in a manner described above for chisel 74. At thistime a lordotic trial 40, FIG. 52, is inserted into the preformedchannels to assess the fit of a proposed implant. If necessary, thechiseling may be repeated for the next larger size and the fit measuredwith an appropriately size trial. Once the trial has been used to assessthe disc space D, to the surgeon's satisfaction, the implant is theninserted using an appropriate inserter tool.

The above steps are repeated on the opposite side of the disc space byremoving the distractor 35, FIG. 51, at this side. The guided boxstarter chisel and finishing chisel may both be modular to accept thequick release handle 80, FIG. 15, and as described above in connectionwith the chisel 74, FIG. 16. The finishing chisel 156 not described asaccepting the quick release handle in FIG. 18, but may also optionallybe configured as the distal end of the chisel 74 to accept the quickrelease handle 80, FIG. 15. The quick connect handle 80 has a threadedbore in the end opposite the sleeve 122 for receiving a slap hammer (notshown). The guided and finishing box chisels as well as the other toolsare color coded to indicate a set of tools that is dimensioned to beused together for a given implant size.

In FIGS. 24 and 25, chisel 186 is substantially the same as tool 74,FIGS. 11-13 except the guide member 188 may be a separate piece and fitswithin the cavity 190 inside the chisel tip 192. The member 188 issecured within the cavity by pin 194 which is press fit to the guidemember 188 in one embodiment. In a further embodiment, the member 188may be one piece with the tip 192. The pin 194 serves as a depth stop tolimit the depth of insertion of the chisel into the disc space. In thevarious figures, protrusions similar to pin 194 serve primarily as adepth stop acting as a positive stop to limit the insertion depth of thechisels, as well as a visual depth limiting indicator. Such a pin orprotrusion need only extend in one direction from the chisel tip. Thischisel is used in the same manner as chisel 74 described above.

In FIG. 26, an alternate embodiment of a guided chisel 196 includes aretractable guide member 198. The chisel 196 includes a shank 200, achisel tip 202 and a knurled handle 204. The tip 202 has two parallelblades 206, 208 and a hollow core 210, FIG. 27. The blades 206, 208 havestraight edges normal to the longitudinal axis 212 and are formed as aconventional box chisel. The side walls 214 of the chisel terminate atthe blade region at non-cutting edges and are recessed as shown from theplane of the edges of the blades. An axially extending slot 216 isformed in each of the side walls 214 and an axially extending slot 218is formed in the top and bottom walls, 220, 222.

The tip 202 has a rectangular bore 224, FIGS. 27 and 28, which is incommunication with the slots 216 and 218. The shank 200 and handle 204have a circular cylindrical bore 225 in communication with bore 224 andthe distal end of the handle 204 and extends through housing 228, FIG.29. Housing 228 is attached to the distal end 226 of the handle 204,FIGS. 26 and 29. The housing 228 has a rectangular through opening 229in communication with bore 225 which also passes through the housing228. The housing is enlarged relative to the handle 204 and isrectangular in end view along the axis 212.

Guide member 198, FIGS. 31 and 32, is metal and rectangular in crosssection and axially slides in the tip 202 bore 224 (FIGS. 32 and 33).The member 198 has a proximal end 230 that has chamfers 232 at the topand bottom surfaces. An axially extending through slot 234 is adjacentto the tip 230. A through bore 236 is in communication with the top andbottom surfaces of the member 198. A threaded axially extending blindbore 238 is in communication with the distal end of the member 198opposite the end 230 and is aligned on axis 240, FIGS. 32 and 33. InFIG. 26, a pin 242 is press fit into bore 236, FIG. 32, of the guidemember 198. The pin 242 passes through the slots 218 of the tip 202,FIG. 27, and is free to axially displace in these slots. The pin 242passes through the slots 218 and protrudes above the top wall 220 andbelow the bottom wall 222 of the chisel tip 202 similar to pin 194 ofchisel 186, FIG. 25. The pin 242 and member 198 are free to axiallydisplace relative to the chisel blades 206, 208, FIG. 27. The top andbottom walls 220 and 222, respectively, have depth indicating indicia244, FIG. 30, for indicating the depth of penetration of the chisel intothe intervertebral disc space D.

In FIGS. 26 and 34, an elongated metal rod 246 has a threaded endportion 248 at the proximal end and a circular disc-like cap 250 at thedistal end. Adjacent to the cap 250 the shaft of the rod has a squarecross section 252.

In FIGS. 26, 36 and 37, a knob 254 which may be stainless steel or othermaterials, is a circular disc with finger gripping grooves 256 on itsouter surface. A circular recess 258 is positioned at one externalsurface of the knob in communication with a square through bore 260. Therecess 258 and bore 260 are in communication with opposite sides of theknob.

The knob is inserted first into the housing 228 opening 229, FIG. 26.The rod 246, FIG. 26, is then inserted into the bore 225 in the housing228 through the recess 258 and bore 260 of the knob 254 and then intothe bore 225 of the handle and shank, FIG. 29. The rod cap 250 sits inthe recess 258. The rod square section 252 is located in the square bore260 and is thus keyed to the knob by the section 252 and bore 260. Thethreaded end portion 248 of the rod is engaged with the threaded bore238 of the guide member 198, FIG. 32. Rotation of the knob 254 rotatesthe rod 246. This rotation engages the threaded end portion of the rodto the threads of the guide member.

In operation, the rotation of the knob by the thumb of a user rotatesthe rod 246 relative to the guide member. This action displaces theguide member 198 to retract the guide member fully into the bore 224 ofthe chisel tip 202 or extend it fully. The retraction and extension isdetermined by the engagement of the pin 242, FIG. 26 with the slots 218of the chisel tip 202. With the member 198 extended, the chisel is usedas a starter chisel to commence chiseling the vertebrae similar infunction to the chisel 74, FIG. 53. the pin 242, FIG. 26, serves tovisually assist the surgeon to determine the depth of insertion of thechisel 196 as well as serve as a stop when the pin abuts the vertebraeas discussed above in connection with the use of chisel 74.

After the proper depth is achieved as determined by the pin 242, theknob 254, FIG. 26, is rotated to fully retract the guide member into thechisel tip 202 bore 224, FIG. 29. At this time the surgeon continues thechisel action as described above in connection with the finishing chisel156, FIGS. 18, 19 and 54. In this case, the same chisel is used with andwithout a guide member to complete formation of the vertebrae channels.The steps for insertion of the implant are otherwise the same asdescribed above.

FIGS. 38-50 show a second embodiment of a chisel 262 with a retractableguide member 264. In FIGS. 38, 41, 42 and 45, chisel 262 includes arectangular in section chisel tip 266, a circular cylindrical in sectionshank 268 and a circular cylindrical handle section 270.

The tip 266 has two parallel blades 272, 274 and a hollow core 276, FIG.46. The blades have straight edges normal to the longitudinal axis 278and are formed as a conventional box chisel. The side walls 280 of thechisel terminate at the blade region at non-cutting edges 273 and arerecessed as shown from the plane of the edges of the blades. An axiallyextending slot 282 is formed in each of the side walls 280 and anaxially extending slot 284 is formed in the respective top and bottomwalls, 286, 288.

The tip 266 has a rectangular bore 290, FIG. 46, which is incommunication with the slots 282, 284 and core 276. The shank 268 andhandle section 270 have a circular cylindrical bore 292 in communicationwith bore 290 and with the distal end of the handle section 270 andextends through reduced diameter cylindrical portion 294 of section 270,FIG. 42.

The reduced diameter portion, FIG. 43, has a pair of identical alignedelongated axially extending slots 296 on opposite sides thereof (onlyone slot being shown). The slots 296 each have a pair of detent grooves298, one groove at each of opposite ends of each of the slots.

In FIGS. 41, 42, 49 and 50, a sleeve 300 slides over the reduceddiameter portion 294 of the handle section 270 and is secured in place.The sleeve 300 has a pair of slots 302 aligned in opposing relation onopposite sides of the sleeve. The slots 302 are aligned with the slots296 and grooves 298 of the reduced diameter portion 294 of the handlesection 270 so that the slots 296 and grooves 298 are visible throughthe slots 302.

A rod 304, FIG. 41, has a collar 306 with a through bore 308. A pin 310passes through the through bore 308 extending beyond the rod on eachside. The pin 310 passes through the slots 302, FIG. 50, and 296, FIG.43, in the respective sleeve 300 and handle portion 294. The rod 304 isinserted into the bores 290 and 292 of the shank 268 and tip 266. Theproximal end 312 of the rod 304, FIG. 41, has a reduced diameter stud314. The stud 314 is attached to guide member 264, FIG. 41, via athreaded bore (not shown) in the guide member 264. The guide member 264is shaped similar to the guide member 198, FIG. 32 except that it has arelatively short threaded bore for receiving the stud 314 instead of theelongated threaded bore of the member 198, which receives the threadedend of the rod 246 of that embodiment. In FIG. 41, the rod stud 314 isattached to the guide member via the mating threads thereof. The rod 304once attached to the guide member 264 does not rotate relative to theguide member.

Guide member 264, FIG. 41, is metal and rectangular in cross section andaxially slides in the tip 266 core 276 and is substantially similar tothe guide member of FIGS. 31 and 32. The member 264 has a proximal endthat has chamfers at the top and bottom surfaces. An axially extendingthrough slot is adjacent to the tip of the guide member. A through boreis in communication with the top and bottom surfaces of the member 264for receiving the pin 314. A threaded axially extending blind bore is incommunication with the distal end of the member 264 opposite the end 316and is aligned on axis 318, FIG. 41. The pin 314 is press fit into boreof the guide member 264. The pin 314 passes through the slots 284 of thetip 266, FIG. 42, and is free to axially displace in these slots. Thepin 314 passes through the slots 284 and protrudes above the top walland below the bottom wall of the chisel tip 266 similar to pin 194 ofchisel 186, FIG. 25. The top and bottom walls have depth indicatingindicia for indicating the depth of penetration of the chisel into theintervertebral disc space D

In operation, the pin 310, FIG. 38, is displaced in directions 312 toretract the guide member 264 fully into the core 276, FIGS. 46 and 47,or to fully extend the guide member as shown in FIGS. 38 and 48. The pin310 in slots 296 and 302 (FIGS. 43 and 49) is displaced axially untilaligned with either of the detent grooves 298, FIG. 43. At this time thepin 310 is rotated to seat the pin 310 in abutment with the surfacesforming the corresponding groove 298. This releasably locks the pin 310in the axial position with the guide member 264 extended or retracted.The chisel in use is used similarly as the chisel of FIGS. 24-37 asdescribed above. The chisel 262 of FIG. 38 is used in a two stepprocedure to first form a channel partially into the vertebrae with theguide member 264 extended until the pin 314 protruding from the tip 266,FIG. 41, abuts the adjacent vertebrae ends. This sets the depth ofpenetration as described previously. The guide member is then retractedand the channel is then finished to its desired depth.

In FIG. 45 a, chisel 262′ has V-shaped cutting blades 272′ and 274′ thesame as that of chisel 74, FIG. 11. The rest of the chisel 262′ is thesame as the chisel 262, FIG. 45. Chisel 262′ is arranged to have aretractable guide member (not shown in FIG. 45 a) similar to that ofchisel 262. Parts with the same reference numbers in FIG. 45 are thesame. Parts with primed reference numerals in FIG. 45 a are similar tothe parts of FIG. 45 with the same reference numerals without the prime.

In FIG. 45 b, chisel 262″ have cutting blades 272″ and 274″ which areinclined relative to the longitudinal shank axis 271. The blade cuttingedges lie in the plane of the top and bottom surfaces of the chisel tip268″ in this embodiment. They may be non-coplanar to the chisel endsurfaces in other embodiments. The edges also lie in a second planenormal to the plane of the top and bottom surfaces. This latter secondplane is inclined at an acute angle to the longitudinal axis 271 asshown in FIG. 45 c. The rest of the chisel 262″ is the same as thechisel 262, FIG. 45. Chisel 262″ is arranged to have a retractable guidemember similar to that of chisel 262, FIG. 45. In the alternative, thischisel may have a fixed guide member as shown for chisel 74, FIG. 11 orchisel 186, FIG. 24. Parts with the same reference numbers in FIG. 45are the same. Parts with primed reference numerals (′) in FIG. 45 a aresimilar to the parts of FIG. 45 with the same reference numerals withoutthe prime.

In the embodiments of FIGS. 11, 45 a and 45 b, the blade(s) terminatesin a point in top plan view, the point either being formed by the bladeas in FIG. 11 or by the blade at a side wall of the chisel tip portionsuch as at side wall 280″ as in FIG. 45 c. The angle of the blade edgesto the longitudinal axis is set at a value that is determined to beoptimal for the chiseling operation.

It will occur to one of ordinary skill that various modifications may bemade to the disclosed embodiments. For example, chisels are describedwith a fixed guide member that is one piece or multiple pieces with thechisel tip and a retractable guide member. In addition, in furtherembodiments, the chisel blades have different configurations. In stillfurther embodiments, the chisel has a an integral one piece handle or areleasable handle in addition to added structure for providing aretractable guide member. It should be understood that these embodimentsof guide members, blade configurations and handle configurations may beemployed in a given embodiment of a chisel in any combination ofdifferent configurations. It is intended that the scope of the inventionis as defined in the appended claims.

1. A chisel for preparing adjacent vertebrae for insertion of a spinalimplant into the disc space defined by the vertebrae, the chiselcomprising: a shank having a longitudinal axis and distal and proximalends; and a bone cutting blade attached to the shank proximal end andhaving a cutting edge lying in a first plane for forming a channel inone of the vertebrae, the blade extending transverse to a second planenormal to the first plane, the second plane containing the longitudinalaxis, the blade having a bone cutting edge facing in a proximaldirection, the cutting edge being non-linear in shape in top plan viewand having an apex in the top plan view, the cutting edge having firstand second cutting coplanar portions in the first plane, each first andsecond edge portion tapering toward the proximal direction.
 2. Thechisel of claim 1 wherein the cutting edge first and second portionstaper toward each other terminating at the apex.
 3. The chisel of claim1 wherein the first and second portions of the blade are symmetricalrelative to the axis and the apex lies on the axis.
 4. The chisel ofclaim 1 wherein the shank at the proximal end is solid with arectangular cross section, the shank having peripheral top and bottomsurfaces and peripheral first and second side surfaces, furtherincluding a chisel guide member one piece with and fixedly secured tothe shank and extending from the shank proximal end coextensive withsaid outer side surfaces juxtaposed with and beyond the blade apex. 5.The chisel of claim 4 wherein the blade has a top surface that iscoextensive and coplanar with the shank top surface and a cutting edgethat tapers distally toward the shank and toward the guide member. 6.The chisel of claim 1 including two of said blades spaced apart so thateach blade is positioned to remove bone from a different vertebra of thetwo adjacent vertebrae.
 7. The chisel of claim 6 wherein the two bladesare symmetrical relative to each other.
 8. The chisel of claim 1 whereinthe shank has peripheral top and bottom surfaces, further including aprojection extending at least from one of the top and bottom surfacesand spaced distally from the blade edge for abutting adjacent vertebraeduring use of the chisel to limit the depth of penetration of the chiselinto said vertebrae disc space.
 9. The chisel of claim 8 wherein theprojections each comprise a portion of a pin inserted in a through borein the shank.
 10. The chisel of claim 1 wherein the shank has a grooveand a shoulder adjacent to the distal end thereof, further including ahandle attached to the shank distal end and including a quick releasesleeve arranged to be releasable secured to the groove and shoulder. 11.The chisel of claim 10 wherein the sleeve includes a pin for mating withthe shoulder to preclude relative rotation of the sleeve and handle tothe shank.
 12. The chisel of claim 10 wherein the handle includes ashaft portion with a plurality of balls arranged in annular array aboutthe shaft portion for radially displacement in corresponding bores, thesleeve having a stepped bore having first and second segments forreceiving the shaft portion along said axis, the first segment forallowing the balls aligned therewith to be radially aligned with andexternal said groove in a first axial position of the sleeve to permitthe shank to be disengaged from the shaft portion and the second segmentfor urging the balls into said groove in a second axial position toreleasably lock the shaft portion to the shank.
 13. The chisel of claim11 including a resilient member coupled to the sleeve for resilientlyurging the sleeve to a quiescent second position to normally lock thehandle to the shank in the quiescent second position.
 14. The chisel ofclaim 13 wherein the shaft portion and the sleeve have juxtaposed spacedshoulders, the resilient member comprising a spring between and abuttingsaid shoulders.
 15. The chisel of claim 1 including a pair of said bladein juxtaposed spaced relation, each blade of the pair for removing bonefrom a different one of the adjacent vertebrae.
 16. The chisel of claim1 wherein the shank has a hollow core at said proximal end facing insaid proximal direction, further including a chisel guide member movablyattached to the shank for selectively extending from the core in adirection toward the proximal end and retracting into the core in adirection toward the distal end.
 17. The chisel of claim 16 wherein saidguide member has a through slot, the shank including a pin fixed to theguide and movably attached to the shank in said slot so that the guidemember can axially displace in said core in opposite directions alongthe longitudinal axis toward and away from the proximal end.
 18. Thechisel of claim 17 wherein the pin protrudes from the shank to provide avisual indication of the depth of penetration of the chisel into thevertebral disc space and provides depth limit means for abutting atleast one of the vertebrae forming a stop for the chisel.
 19. The chiselof claim 16 including guide member displacement means for selectivelymanually respectively extending and retracting the guide member from andinto the core.
 20. The chisel of claim 19 wherein said displacementmeans comprises a first elongated member attached to the guide memberand having a portion extending into the handle, and a rod displacementarrangement coupled to the elongated member portion for axiallydisplacing the first rod toward and away from the proximal end.
 21. Thechisel of claim 20 wherein the rod is releasably attached to the guidemember.
 22. The chisel of claim 21 including threads for rotationallycoupling the rod to the guide member, and a knob connected to the rodfor rotating the rod relative to the guide member, the knob having afixed axial position on the handle such that rotation of the knobdisplaces the guide member via the threaded engagement of the rod to theguide member.
 23. The chisel of claim 22 wherein the knob is keyed tothe rod to rotate the rod with rotation of the knob.
 24. The chisel ofclaim 23 wherein the handle has a slot receiving the knob, the receivedknob for manual engagement by a thumb.
 25. The chisel of claim 1 whereinthe shank at the proximal ends has at least one through slot forreceiving bone chips during use of the chisel.
 26. The chisel of claim20 wherein the rod displacement means includes a transversely extendingelongated member attached to the first rod at the first rod end distalthe guide member and detent means attached to the handle for receivingthe elongated member for selectively releasably securing the elongatedmember in guide member retracted and extended positions.
 27. The chiselof claim 26 wherein the detent means comprises a slot in the handle forreceiving the elongated member, the slot having first and second axiallyspaced channels each for selectively receiving the elongated member. 28.The chisel of claim 27 including a sleeve over the handle at the slotincluding a further slot juxtaposed with the handle slot
 29. A chiselfor preparing adjacent vertebrae for insertion of a spinal implant intothe disc space defined by the vertebrae, the chisel comprising: a shank,the shank having a longitudinal axis and having distal and proximalends, the proximal end having top and bottom surfaces and opposing firstand second side surfaces; and first and second juxtaposed spaced bonecutting blades, each blade having a cutting edge lying in a first planeat the shank proximal end in a plane parallel to the respective top andbottom surfaces, each blade edge facing in a proximal direction andextending transverse to the longitudinal axis in the first plane fromthe first side surface to the opposing second side surface, the edges ora tangent thereto each lying in a second plane normal to the firstplane, the second plane being inclined relative to the axis and relativeto the opposing side surfaces in a direction toward the proximal end,the edges each having a portion in which the tangent thereto intersectsa second side surface in top plan view at an acute angle.
 30. The chiselof claim 29 wherein the shank has a hollow core and including a guidemember movably secured to the shank in the core and having a firstretracted position located within the shank core and a second extendedposition extending beyond the shank at the proximal end for abuttingadjacent vertebrae in the disc space during use.
 31. The chisel of claim29 including a pin passing through an axially extending slot in theshank and through the guide member for limiting the axial displacementof the guide member.
 32. The chisel of claim 30 wherein the pinprotrudes from the shank to provide a visual indication of the depth ofpenetration of the chisel into the vertebral disc space and to providedepth limit means for abutting at least one of the vertebrae forming astop for the chisel during use.
 33. The chisel of claim 29 includingguide member displacement means for selectively manually respectivelyextending and retracting the guide member from and into the core. 34.The chisel of claim 29 further including a handle secured to the shankdistal end and wherein said guide member displacement means comprises afirst rod attached to the guide member and having a rod portionextending into the handle, and a rod displacement arrangement coupled tothe rod portion for axially displacing the first rod toward and awayfrom the proximal end.
 35. The chisel of claim 34 wherein the rod isreleasably attached to the guide member.
 36. The chisel of claim 35including threads for rotationally coupling the rod to the guide member,and a knob connected to the rod for rotating the rod relative to theguide member, the knob having a fixed axial position on the handle suchthat rotation of the knob displaces the guide member via the threadedengagement of the rod to the guide member.
 37. The chisel of claim 36wherein the knob is keyed to the rod to rotate the rod with rotation ofthe knob.
 38. The chisel of claim 37 wherein the handle has a slotreceiving the knob, the received knob for manual engagement by a thumb.39. The chisel of claim 29 wherein the shank at the proximal ends has atleast one through slot for receiving bone chips during use of thechisel.
 40. The chisel of claim 34 further including a handle secured tothe shank distal end wherein the rod displacement means includes atransversely extending second rod attached to the first rod at the firstrod end distal the guide member and detent means attached to the handlefor receiving the second rod for selectively releasably securing thesecond rod in guide member retracted and extended positions.
 41. Thechisel of claim 40 wherein the detent means comprises a slot in thehandle for receiving the second rod, the slot having first and secondaxially spaced channels each for selectively receiving the second rod.42. The chisel of claim 41 including a sleeve over the handle at theslot including a further slot juxtaposed with the handle slot
 43. In amethod for preparation of a disc space for insertion of a spinal implantinto the disc space between adjacent vertebrae, the steps comprising:initially removing a first portion of at least one of two adjacentvertebrae of the disc space with a first chisel with an extended guidemember to form at least one partial channel in the at least onevertebra, the guide member for bearing against the adjacent vertebraeand guiding the chisel during the removing; and then removing a furtherdeeper second portion of the at least one adjacent vertebrae with asecond chisel guided by first channel portion, the second chisel havingno guide member, to form the at least one partial channel into at leastone complete channel for receiving a spinal implant inserted into thedisc space, the further portion being aligned with and extending said atleast one channel to a depth into the disc space an amount sufficient toform said complete channel.
 44. The method of claim 43 including formingsaid at least one partial channel and said at least one complete channelin each of said adjacent vertebrae with the same chisel.
 45. The methodof claim 44 wherein said removing a further portion of the at least oneadjacent vertebrae with a second chisel includes retracting the guidemember of the first chisel into the first chisel to form the firstchisel into the second chisel.
 46. The method of claim 43 wherein saidremoving a further portion of the at least one adjacent vertebrae with asecond chisel includes removing the first chisel from the formed atleast one partial channel in the at least one vertebra and theninserting the second chisel into the formed at least one partial channelwherein the at least one partial channel guides the second chisel duringthe insertion.
 47. The method of claim 46 further including the stepsof: performing a discectomy on the disc space; distracting the discspace at a first side of the spinal column; removing disc material fromthe disc space on the contralateral side of the disc space opposite thefirst side and preparing the end plates of the vertebrae with a rotatingscraper at the contralateral side; performing the steps of claim 45 onthe prepared end plates of the contralateral side; determining theheight of the disc space between the channels in the adjacent vertebraefor determining the associated implant size to be inserted into the discspace; inserting the implant into the formed channels and disc space onthe contralateral side of the disc space; removing the distractor; andrepeating the above steps on the first side of the disc space.
 48. Achisel for preparing adjacent vertebrae for insertion of a spinalimplant into the disc space defined by the vertebrae, the chiselcomprising: a handle; a shank having a longitudinal axis and distal andproximal ends, the handle being secured to the distal end; and a pair ofbone cutting blades attached to the shank proximal end, each bladehaving a cutting edge lying in a plane for forming a channel in adifferent one of the adjacent vertebrae, the blades extending transverseto the longitudinal axis with their bone cutting edges facing in aproximal direction; the shank at the proximal end being solid with arectangular cross section, the shank having peripheral top and bottomsurfaces and peripheral first and second side surfaces, furtherincluding a solid rectangular chisel guide member one piece with andfixedly secured to the shank and extending from the shank proximal endcoextensive with said peripheral side surfaces and juxtaposed with andbeyond each of the blades.
 49. The chisel of claim 48 wherein the bladeseach have at least a portion that extends in a direction transverse toand at an acute angle to the longitudinal axis in top plan view andjuxtaposed in mirror image relation.
 50. A chisel for preparing adjacentvertebrae for insertion of a spinal Implant into the disc space definedby the vertebrae, the chisel comprising: a handle; a shank having alongitudinal axis and distal and proximal ends, the handle being securedto the distal end; a pair of bone cutting blades attached to the shankproximal end, each blade having a cutting edge lying in a plane forforming a channel in a different one of the adjacent vertebrae, theblades extending transverse to the longitudinal axis with their bonecutting edges facing in a proximal direction; the shank at the proximalend having a hollow core; a chisel guide member movably secured to theshank in the core having extended and retracted states for beingselectively juxtaposed with and beyond each of the blades in theextended state for bearing against the adjacent vertebrae and forwithdrawing into the core in a retracted state; and means coupled to thehandle for selectively retracting and extending the guide member to therespective retracted and extended states.
 51. The chisel of claim 50wherein the means for selectively retracting and extending includes arod connected to the guide member in the core for axially displacing theguide member along the longitudinal axis of the shank, and a handlemember secured transversely to the rod at a rod end distal the guidemember and extending beyond the handle for manual gripping.
 52. Thechisel of claim 51 including detent means for releasably holding thehandle member in the retracted and extended states.
 53. The chisel ofclaim 52 wherein the detent means comprises a longitudinal slot in thehandle and circumferential detent grooves axially spaced incommunication with the slot for selectively rotatably receiving thehandle member.
 54. The chisel of claim 50 wherein the means forselectively retracting and extending includes a rod threaded to theguide member and located in the core for axially displacing the guidemember along the longitudinal axis of the shank, and a knob rotatablysecured to the shank and secured to the rod distal the guide member forrotating the rod threads relative to the guide member threads to therebydisplace the guide member during the rotation of the rod.
 55. The chiselof claim 54 wherein the handle has a slot, the knob being located in theslot.
 56. A chisel for preparing adjacent vertebrae for insertion of aspinal implant into the disc space defined by the vertebrae, the chiselcomprising: a handle; a shank having a longitudinal axis and distal andproximal ends, the handle being secured to the distal end; and a bonecutting blade attached to the shank proximal end and having a linearcutting edge for forming a channel in one of the vertebrae, the bladehaving at least one portion inclined to the longitudinal axis and havinga bone cutting edge facing in a proximal direction, the bladeterminating at a point in top plan view.
 57. The chisel of claim 1further including a handle attached to the shank distal end.
 58. Thechisel of claim 1 further including a handle releasably attached to theshank distal end.